1. Field of the Invention
The invention relates to a resist lower layer film (bottom coating)-forming composition, a polymer, a resist lower layer film, a pattern-forming method, and a method of producing a semiconductor device.
2. Discussion of the Background
A semiconductor device production process has utilized a lithographic microfabrication process using a photoresist composition. The microfabrication process includes a step of forming a resist film on a substrate, a step of exposing the resist film by applying radiation (e.g., ultraviolet rays) to the resist film, a step of developing the exposed resist film, and a step of etching the substrate using the resulting resist pattern as a protective film. In recent years, radiation (e.g., ArF excimer laser light (193 nm) or EUV (13.5 nm)) having a wavelength shorter than that of KrF excimer laser light (248 nm) has been used for a semiconductor device production process along with an increase in the degree of integration of semiconductor devices. When using short-wavelength radiation, however, it may be difficult to form an excellent fine pattern due to diffused reflection from the substrate, standing waves, and the like. In order to deal with this problem, a method that forms a resist lower layer film (e.g., bottom anti-reflective coating (BARC)) between the resist film and the substrate has been extensively studied.
An inorganic resist lower layer film formed of titanium, titanium dioxide, titanium nitride, chromium oxide, carbon, α-silicon, or the like, and an organic resist lower layer film formed of a light-absorbing substance and a polymer compound have been known as the resist lower layer film. A vacuum deposition system, a CVD system, a sputtering system, or the like is required to form the inorganic resist lower layer film, while a special system is not required to form the organic resist lower layer film. Therefore, the organic resist lower layer film has been extensively studied. For example, U.S. Pat. No. 5,919,599 discloses an acrylic resin resist lower layer film that includes a hydroxyl group (crosslinkable group) and a light-absorbing group in one molecule, and U.S. Pat. No. 5,693,691 discloses a novolac resin resist lower layer film that includes a hydroxyl group (crosslinkable group) and a light-absorbing group in one molecule.
It is desired that an organic resist lower layer film-forming composition have a high light/radiation absorbance, does not undergo intermixing with a resist film, can prevent a situation in which a low-molecular-weight component is diffused from the resist lower layer film-forming composition to the resist film during application or heating (drying), and have a high dry etching rate as compared with the resist (see Proc. SPIE, Vol. 3678, 174-185 (1999) and Proc. SPIE, Vol. 3678, 800-809 (1999), for example). A resist lower layer film-forming composition is also desired to exhibit higher resolution, form a rectangular resist pattern having a smaller pattern size, ensure that the resist lower layer film exhibits good adhesion to the resist film, and exhibit high pattern collapse resistance along with an increase in the degree of integration of semiconductor devices.
In particular, development of a resist lower layer film-forming composition that can implement a high etching selectivity ratio with respect to the resist film and the substrate when forming a pattern by dry etching, and can form a resist lower layer film that exhibits high pattern collapse resistance, and a resist lower layer film that has the above properties has been strongly desired for the current semiconductor device production process in order to deal with a decrease in pattern size.